Sony's original claim that your CDs would be good forever was a little optimistic. CDs and DVDs, especially CDRs and DVDRs are susceptible to literal bit-rot. Some cheap CDRs don't even last five years.
Forgotten sockets will also pose a problem. It's not very easy to get hold of a board with an EISA slot as it is. Imagine how hard it is going to be to find a motherboard with PATA in 25 years. Connecting wireless devices that use a long dead proprietary protocol may be even harder.
More and more, our digital lives are being stored on the Internet. Not everything about a person can be found on one machine. It would take masses of data collected from numerous sources to hope to build a profile on a unknown person. In the same vein, having our data scattered far and wide would increase the chances of at least something being found, rather than all your eggs in one basket.
More and more, operating systems are overstepping the mark with their role in computing. It has become common for the Operating System to dictate how and where your software will work, or not work. Microsoft Windows will enter a reduced mode when it detects a change in hardware, and has to be reactivated. There is no guarantee that in the future, the servers needed to activate an old unsupported version of Windows will even be around anymore, let alone Microsoft themselves in their current form.
Some operating systems such as Mac OS X or Amiga OS will not boot on anything but their original hardware. In the near future TPM modules may severely restrict the ability to access old and forgotten data without the original hardware. Advances in computing in the future may mean that all this can be emulated and hacked, but that is still based on the notion that some selfless hacker will do the work, because Microsoft, Sony or Apple certainly won't.
Companies have been faster to establish themselves in the digital realm then the government, and the law. We have seen with shocking speed, large corporations move in and start laying down their own laws how they see fit. If you want their goods, (and you do) you have to agree to any terms they dream up, and there is not enough governing agencies or laws to protect you in the same way you have protection against unlawful advertising and practices on the TV and in store.
What's more, corporations are pushing the government to create laws that protect them and not you, against these practices. The DMCA means that in North America it is a crime to reverse engineer any protection schemes to provide interoperability. In the near future, there may be attempts to produce software or hardware to ensure that data that is falling out of accessibility (due to corporations discontinuing support for products and services), may be blocked by legal action; ensuring that only the parent company has the key to unlock your data, and only when it suits them.
It goes without saying that as the speed of processing increases, cracking DRM will be easier, especially if quantum computing becomes a reality. That said, DRM still places a lock on our digital data, which is getting increasingly difficult to break, even to the point of being illegal (as above).
Magnetic media fades over time. Though this is obviously stated, it is last in this list for a reason. Even if solid-state hard disks become common, the data on them is still subject to many of the problems listed above; namely DRM, and proprietary software / formats. The data could be around forever, but that still implies little to its accessibility. Many floppy disks and magnetic media from the 80s is beginning to fade away already.
Data that never dies
Surely all of this highlights the need for Open Source software like Linux? However, this is still based on the na´ve assumption that just because the code is open, it will be around forever. People still need to host and store the code and provide access via the Internet, often underfunded. If you can't get the code easily anymore, how open is it?
More so, Linux, and nearly all Open Source software runs on proprietary processors and hardware. It can be recompiled to run on other arcs, provided that you have the source, the compiler, and the compiler is updated for the new arc. (and the compiler is compiled and running on the new arc) In the far future, where so much has been changed, even old Linux source code and data could be so alien to new computers that is no longer usable. That is also based on the assumption that open source operating systems will even be possible in the future, given the barrage of attacks from the law, Trusted Computing and proprietary hardware that is protected by DMCA. Open Source software may very well be either the dominant type of software in the future, or nearly wiped out. Its future is not guaranteed at all just because it is open.
If you have something you want to say to the future, then you're better off writing it on a piece of paper and putting it away safely. The way things are going, we will be lucky if any of our digital data is readable in 100 years, but your piece of paper could easily still be around.
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